For such interior trimming pieces, in particular in modern motor vehicles there arises the object of not only being lightweight and environmentally friendly, but also affording opportunities for the passage of airbag modules arranged behind the interior trimming piece.
Thus a generic interior trimming piece for motor vehicles is known, which has a plastic substrate and, connected thereto, a metal reinforcing piece provided with a hinge sheet for bridging a channel for passage of an airbag in at least one region. This metal reinforcing piece is e.g. a sheet metal piece which is riveted to the plastic substrate and which has a predefined bending edge, so that in case of release of an airbag this bending edge serves as a hinge for an airbag flap, while the plastic substrate is torn open in the region of the channel for passage of the airbag.
The metal piece here also has the object of providing a rigid means for bridging the channel for passage of the airbag during normal running of the vehicle.
Disadvantages of known interior trimming pieces, however, often lie in the controlled hinging of the flap, that is, opening of the channel for passage of an airbag when the airbag is released. Here, firstly it is sensible to at least roughly control the angle of opening of the flap, and secondly there should be a very firm grip between plastic substrate and metal reinforcing piece, so that no metal pieces can possibly enter the interior of the vehicle accidentally.
For this purpose there must be sufficient strength of the bond between metal reinforcing piece and plastic substrate to accomplish the highly dynamic forces when the airbag is fired without accidental deformation or fractures of the plastic substrate. Thus e.g. even the formation of a “bulge” with insufficiently rigid constructions is a serious drawback.
On the other hand, there should not be an unsafe result in the “head impact” test on the instrument panel due to too rigid a design e.g. of the plastic substrate, which furthermore can be very expensive and is weight-intensive in the construction. That is to say, there must be sufficient elasticity of the interior trimming piece/instrument panel in order not to cause serious injuries if passengers strike the instrument panel.
A disadvantage of all generic interior trimming pieces known in the state of the art is also that a join of the plastic substrate to the metal reinforcing piece is visible because, particularly e.g. after intensive solar radiation, arches or rivet heads stand out through a decorative layer which seals off from the interior of the motor vehicle.